1. Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544
2. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025
3. Polyera Corporation, Skokie, Illinois 60077
4. Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742, Korea